MOT behavior / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

MOT behavior

Move Thread

LAN_403

Killa-X

Fri Nov 26 2010, 06:09PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Maybe its my rig, maybe its something more in depth.

This is how I've done it in the past.

This is how I do it now.

If I'm correct, both setups are 100% the same. Just different layout.

First, I've been told its OK to have the metal shells of the capacitors touch. Is this true? Because my new design allows them to make contact with each other.

The ONLY other thing, I can think of, as to why my arcs are acting shitty, is Weather. Is it possible, since its 28F outside, that the arcs will act different because arcs are hot, and its cold? I never had arcs that try to blow down and arc to the grounded shell of my MOT case. Lucky enough I use insulators, so it broke the arc.

pauleddy

Sat Nov 27 2010, 01:28AM

Registered Member #2909 Joined: Wed Jun 09 2010, 12:31AM
Location: fort belvoir, Va USA ( south of DC)
Posts: 145

did you check if you caps hace internal diodes , some of mine have one inside of them test connection crom each contact to the case if one of the is grounded

Xray

Sat Nov 27 2010, 04:13AM

Registered Member #3429 Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288

pauleddy is correct. Some Microwave Oven caps have internal diodes and/or bleeder resistors that may be causing problems for you. Another thing to consider when attempting place hv transformers or caps in series is the breakdown voltage rating of the insulation. For example, I recall a young, inexperienced electronic experimenter on some forum (maybe 4HV?) asking if he can place 4 MOT's in series in order to get a total of 10KV output! Yes, he may get 10KV for a few millisenconds before an arc forms from one of the windings to the core of one or more of the MOT's. It sounds logical to be able to do this, but in practice it will not work due to the breakdown voltage rating of the MOT insulation. It was designed to handle 2500 VAC, NOT 10KV AC! Therefore keep this in mind when trying to tie together hv transformers and/or capacitors.

Killa-X

Sat Nov 27 2010, 04:37AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Yup. This dual stack has been linked for 2100VAC or so, and i have at least 2 in series to add up for that. I had this for awhile, and it never failed me.

My only possible guess is the wind. I understand how little wind can really screw an arc. But, I had the garage closed, I felt no wind at all. Yet, outside, it was extreamly windy. The only thing I can think of, is the wind pushing hard on the garage door, causing a change in room pressure, which caused my arcs to shoot down instead of up. Because when I drew these arcs, only 5 inches out, it usually arcs in a ^ shape until the breaker tripped. Well, it went straight down. like a V. And my insulators broke it before it could burn the acrylic.

guess I try again tomorrow and hope its not windy.

Is it possible the cold 30F air can effect an arc?

I did try redoing the bank, ripping it apart, and having nothing touch. It still sucked, because the arcs kept rushing down instead of up. Even when I tri to pull an arc up, it would break near instantly. Usually I can slow-draw it to 2ft. But i get 3" and it died. But if i pulled FAST, i got the 2ft.

{b]Update[/b]

I tried again today, no wind. The arcs do work a lot better. So i guess the pressure on the door did effect the room, even though I my self personally felt no draft. Was able to arc good on it, and the arc ended up shifting over, to the other terminal, and made a big loud BANG because the capacitors discharged through the arc xD Had this happen before, so I didn't think a capacitor failed.

Kiwihvguy

Tue Dec 28 2010, 09:34AM

Registered Member #3395 Joined: Thu Nov 04 2010, 08:42AM
Location: Christchurch, New Zealand
Posts: 193

Xray wrote ...

For example, I recall a young, inexperienced electronic experimenter on some forum (maybe 4HV?) asking if he can place 4 MOT's in series in order to get a total of 10KV output! Yes, he may get 10KV for a few millisenconds before an arc forms from one of the windings to the core of one or more of the MOT's. It sounds logical to be able to do this, but in practice it will not work due to the breakdown voltage rating of the MOT insulation. It was designed to handle 2500 VAC, NOT 10KV AC! Therefore keep this in mind when trying to tie together hv transformers and/or capacitors.

Yeah, MOT's are generally designed only to handle the voltage they generate but you can push it so that the insulation is insulating ~4kVAC (eg. in a dual MOT stack) but I was wondering if I could make a quad MOT stack, but under oil? With an output of 8kVAC, the oil should withstand it? If so, what kind of oil should I use? Or do I have to worry about it internally arcing, like in the actual winding? Does that happen? Feel free to correct me and tell me what's right...

Dr. ISOTOP

Tue Dec 28 2010, 10:30PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Quad packs of MOTs in oil are doable, but messy. Use mineral oil or transformer oil if you want to do it.
Alternatively, you can use a dual MOT stack with a doubler - less power, but no submersion needed.

ubuntupokemoninc

Tue Dec 28 2010, 11:57PM

Banned on 1/22/2011 for repeated rule violations after multiple warnings.
Registered Member #3299 Joined: Sat Oct 09 2010, 08:11PM
Location: Bantown, USA
Posts: 220

queston were do you get those insulators?

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob